Turbine cooling cap structure



July 5, 1960 J. N. MARONE TURBINE comma CAP STRUCTURE Filed Jan. 3, 1956 mum u m 3 a ,.||-||..|1/ f C I. f TIL M j a %F 40W I m.- m

INVENTOR. \JDFIEPH N. MARDNE ATTORNEY United States Patent 2,943,340 TURBINE COOLING CAP STRUCTURE Joseph N. Marone, Hawthorne NJ. assignor to Curtiss- Wright Corporation, a corporation of Delaware Filed Jan. 3, 1956, Ser. No. 557,050

. 1 Claim. (Cl. 253-3915) This invention relates to gas turbines and particularly directed to a' cooling cap structure for the rotor of a gas turbine.

The invention has been particularly. designed for a gas turbine driven by the combustion gases of a pistontype reciprocating enginefor example a gas turbine such as illustrated in Patent No. 2,607,189, granted August- 19, 1 952.

In such a power plant the gas turbine exhausts into ahead or duct and in order to cool and shield the turbine rotor from the exhaust gases a stationary cooling cap is disposed over the exhaust side of the turbine rotor disc. An object of the present invention comprises the provision of a novel and simple cooling cap structure.

Cooling air is supplied to the turbine cooling cap via passages through the rotor disc between the root ends of the rotor blades. In order to minimize any leakage of exhaust gases into the cooling cap through the clearance between the cooling cap and the rim of the turbine rotor disc the cooling cap is provided with a double walled construction such that any exhaust gases tending to leak into the cooling cap are drawn ofi through the interwall space formed by said double wall construction. In the past difliculty has been experienced in supporting the double walls of the cooling cap because of differential expansion therebetween. An object of the present invention comprises the provision of a novel and single cooling cap support structure eliminating ditficulties previously encountered because of difierential expansion between the cooling cap walls.

Other objects of the invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

Fig. 1 is an axial sectional view along line 1-1 of Fig. 2 and illustrating a gas turbine and cooling cap combination embodying the invention; and

Fig. 2 is a top view of Fig. 1 with the exhaust hood and exhaust hood clamp removed.

Referring to the drawing a gas turbine is illustrated as comprising a stator 12 having an annular nozzle construction 14 through which combustion gases are directed against the blades 16 extending radially outwardly from the rim 17 of a turbine rotor 18. The rotor '18 is journaled in the stator by hearing means not shown. The gas turbine 10 is designed for use in the power plant disclosed in the aforementioned patent. Thus the turbine motive fluid constitutes the hot exhaust gases of an internal combustion engine and the turbine rotor 18 is drivably connected to the crankshaft of said engine.

The exhaust gases discharge fi'om the turbine rotor blades 16 into an exhaust hood or duct 20 communicating with the surrounding atmosphere. The exhaust duct or hood 20 being secured to the stator 12 by a clamping means 22 for example as illustrated in copending application Serial No. 224,167, filed May 2, 1951, now Patent No. 2,811,331. In order to shield the turbine rotor 18 and to cool said rotor a cap 24 is supported over the turbine by a plurality of circumferentially-spaced' spokes 26 extending radially inwardly from ring means 28 secured to'said stator 12 by the clamping means 22.-

T The inner ends of the spokes 26 are connected together by a central bracket 30 disposed over the hub of the turbine rotor 18. The cap 24 is co-axial with the turbine rotor 18 and the rim of the cap is disposed adjacent to the rotor rim and the bottom 33 of the cap is spaced fromthe rotor exhaust face whereby the cap 24 forms a chamber 32 over the exhaust face of said rotorand said cap and cooperates with the adjacent por tion of-the exhaust hood to form an annular exhaust passage-portion 35 across which the spokes 26 extend.

Cooling air is supplied to the turbine rotor for flow throughpassages-36 extending through the turbine rotor 18 between the root ends of the turbine rotorblades 16. This cooling air discharges into the cap chamber 32; and from said cap chamber said air discharges into the exhaust duct 20 through a discharge conduit 38.

formed on the cap 24. I

Hot 'exh'austgases discharging from the turbine rotor blades tend to leak into the cooling cap chamber 32 through the clearance 40 between the rotor rim and the adjacent rim of the stationary cooling cap 24. Such leakage of hot exhaust gases into the cooling cap chamber 32 is obviously objectionable in that it raises the rotor temperature. To minimize such leakage the cooling cap 24 and its discharge conduit 38 are provided with a 'hollow double wall construction. Thus the cooling cap hollow double wall comprises an outer wall 42 and an inner wall 44 adjacent to but spaced from the outer wall so as to leave a space therebetween. At the cooling cap rim the hollow interior of the cooling cap double wall opens to the clearance 40 between said rim and the adjacent rim portion 17 of the rotor. At its end connected to the cooling cap 24 the hollow interior of the double wall of the cooling cap discharge conduit 38 communicates with the hollow interior of the cooling cap double wall. The other downstream end of hollow interior of the cooling cap discharge conduit double wall is open so that the exhaust gases flowing through the exhaust duct 20 over the discharge conduit end 45 fiunction as an ejector to draw gas flow through said hollow conduit wall. In this way any exhaust gases tending to leak into the cooling cap chamber 32 are drawn ofi through the hollow wall structure of the cooling cap 24 and its discharge conduit 38.

In order to support the cooling cap outer and inner walls 42 and 44 each spoke 26 is provided with a pair of adjacent bushings or sleeves 52 and 54 slidably mounted thereon. The outer cap wall 42 is secured to each of the outer sleeves 52 as by welding and the inner cap wall 44 is similarly secured to each of the inner sleeves 54. In this way the two walls 42 and 44 of the cooling cap are co-axially supported by the spokes 26 and yet the rim portions 56 and 58 of the Walls 42 and 44 are free to expand and contract relative to each other as a result of relative thermal expansion and contraction of said walls. This freedom whereby the two cooling cap walls 42 and 44 are free to expand and contract relative to each other eliminates stresses which would otherwise be induced in said walls as a result of unequal heating and cooling of said walls.

An inner cap 60 is also supported on the spokes 26 by sleeves 62 slidablyv mounted on said spokes, said inner cap being disposed over the central bracket 30.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be madelt herein without departing from the spirit or scope thereof. I

aim in the appended claims to cover all such modifications. V

I claim as my invention:

' A, gas ,t-urbinecomprising -a ;turbi3ae rotorahaving "a rirnportionand having a'plurality of cireumferen-tially ancespace'rela-tion, ;to said rotor rim portion so. that the bottom of the innenwall of the cup-shaped cap is spaced 7 from said rotor exhaust face to form a chamber over said sid'e'and with the outer wall of 'said eap1being spaced from the exhaust duct toform an annular ex V haust Z'passage therebetween, the hollow space between the cap double Walls opening at the cap rim portion to the clearance space between said portien and the rotor rim portion; said capsupporting means comprising a plurality of circumferentiallyaspaced spokes secured to said stator structure and extending Iradially inwardly across saidannul'ar passage; 21 pair of adja ent but independently slid'able sleeves on each spoke with "the radially outer sleeve of each pairrbeing connectedtosaidcap V outer wall and the radially inner sleeve of eachpair being connected to said capiinner wall; means tor supplying cooling air to said cap chamber; and a hollow double-walled cooling air discharge conduit having spacedapart inner and outer walls, said conduit extending from the bottom of said fco'olin'g cap with the inner wall of said conduit opening through ;in ner wall of said cap to provide fluid communication between said cap chamber and the interior of said: conduit inner wall, the-discharge end efsaideenduit tenn'inating withintsaid exhaust duct for discharging saidscap cooling air into saidfrluc't and the hol-low spaceibetween the conduit doublewalls'cernmunicating'ht one end with V the hollow space between said cap double walls and at its'other end opening into said exhaust duct.

References Cited in the fileof this patent UNITED STATES'PATENTS; 7 2,234,751 Gibson Mar;' ,1941", 2,234,767 Larrecq Mar; 11, 1941; 7 2,370,192 Reeves Feb. 27 ,-194s' 2,465,846 Clegern, Mar.; 29, 1949' 2,620,157 Morley Dec. 2,1952

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